<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 父容器样式 */
        .container {
            width: 600px;
            height: 600px;
            border: 1px solid black;
            margin: 0 auto;
        }

        /* 子元素的样式 */
        .container div {
            width: 33%;
            height: 33%;
            border: 1px solid black;
            float: left;
        }
    </style>
</head>

<body>
    <!-- 搭建页面结构 -->
    <div class="container">
        <div></div>
        <div></div>
        <div></div>
        <div></div>
        <div></div>
        <div></div>
        <div></div>
        <div></div>
        <div></div>
    </div>
</body>

</html>